Health conditions can be checked by analyzing, for example, a specific component in the blood. Recently, analysis apparatuses of a relatively compact size have been developed for executing the component analysis. Some of the analysis apparatuses have a fluid agitation function of mixing the blood and a diluting fluid or mixing the diluted blood and a reagent, for performing the component analysis.
FIG. 18 depicts a cartridge X and an agitation arm 96 employed in a conventional fluid agitation method (see patent document 1 cited below). A main body 91 of the cartridge X includes a dilution chamber 92 for diluting blood 94 therein. The blood 94 introduced into the dilution chamber 92 is agitated with a diluting fluid 95. For performing the agitation, agitation particles 93 bearing magnetism are loaded in advance in the dilution chamber 92. The agitation arm 96 includes a pair of magnets spaced from each other, to be rotated about an axial center in a predetermined direction. When the agitation arm 96 rotates, the magnetic force of the respective magnets drives the agitation particle 93 to circulate, thereby mixing the blood 94 and the diluting fluid 95.    Patent document 1: Japanese Patent No. 3135057
Generally, only a trace amount of blood 94 (for instance, in the order of μL) is used for the component analysis. Accordingly, the agitation particle 93 must be minute in size. Also, the agitation particle 93 must not have such nature that disturbs the analysis of the specific component of the blood 94. However, employing the agitation particle 93 that satisfies such requirements leads to an increase in cost of the cartridge X. In the case, especially, where the cartridge X is of a disposable type, the increase in cost constitutes a major obstacle to regular practical use of the cartridge.
The conventional fluid agitation method has another drawback. As stated above, the circular movement of the agitation particle 93 is caused by magnetic force (non-contact force). Accordingly, the movement of the agitation particle 93 may fail to properly follow up the movement of the agitation arm 96, because of resistance of the blood 94 and so forth. This phenomenon becomes more prominent, in particular, with the increase in rotation speed of the agitation arm 96. Such failure leads to compromise in agitating force, thereby prolonging the time required for the specimen  analysis.